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Abstract

Department of Urban and Environmental Engineering (Environmental Science and Engineering)Gwangyang, Jinhae, Busan, and Ulsan Bay were designated as special management sea areas due to active industrial activities, and various pollutants, including heavy metals, were discharged, resulting in higher contamination of sediments than in other areas. Since heavy metals accumulated in sediments are released according to mobility and can have an adverse effect on the ecosystem depending on their mobility, various chemical forms should be considered to accurately evaluate their impact on the environment. In this study, 67 sediments were collected from four regions and extracted by applying BCR sequential extraction. After that, 11 heavy metals (Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, V, and Zn) in sediments were analyzed by inductively coupled plasma-optical emission spectrometer (ICP-OES). Based on these results, the concentration and fraction distribution of heavy metals were investigated, characteristics of pollution patterns by region were identified, and ecological risk was evaluated using three indices such as individual contamination factor (ICF), risk assessment code (RAC), and modified potential ecological risk index (MRI). Cd and Mn had the highest concentration in Jinhae and Gwang bay, respectively, and showed the tendency to increase the F1 fraction as the concentration increased. Cu and Pb had the highest concentration in Busan bay and shows the tendency to increase the F2 fraction as the concentration increased. Zn also had the highest concentration in Busan bay, and as the concentration increased, the non-residual fraction increased. Other heavy metals had a high proportion of F4 fractions. Also, characteristics of pollution patterns were influenced by regional characteristics and industrial complexes, and it could be confirmed in correlation analysis and PCA. ICF showed that among the four regions, Cd had the highest ecological risk in Jinhae bay, Mn in Gwangyang bay, Cu and Zn in Busan bay, and Pb in Ulsan bay. Other heavy metals showed a low level of ecological risk in all regions. In RAC, among the 11 heavy metals, Cd and Mn showed higher mobility and bioavailability than other heavy metals. Especially in Jinhae bay, the ecological risk of Cd was the highest, and in other bays, Mn showed the highest ecological risk. In MRI, six sites (four sites in Jinhae bay and two sites in Busan bay) were evaluated as a moderate level of ecological risk, and Cd contributed the most to determining the MRI value in almost sites. It means Cd could adversely affect the aquatic environments in all regions. Therefore, it is needed to be careful of the ecological risk caused by Cd.ope